1. Field of the Invention
The present invention relates to a control system and a control method of a GDI (Gasoline Direct Injection) engine.
2. Description of Related Art
In general, the fuel system of a GDI engine is equipped with a low-pressure pump that is operated by a motor to supply fuel onto a fuel rail in a fuel tank and with a high-pressure pump, which is operated by the camshaft, on a head cover.
Further, injectors that inject fuel into combustion chambers, respectively, are mounted and a pressure sensor that detects the internal pressure of the fuel rail is mounted on the fuel rail.
The fuel supplied to the engine from the fuel tank by the low-pressure pump is pressurized to a predetermined pressure, about up to 120 bar, by the high-pressure pump that is operated by a fuel pump cam, and then supplied to the fuel rail.
The pressure sensor mounted on the fuel rail detects the pressure in the fuel rail and provides the information about the pressure to a control unit, and the control unit feedback-controls the fuel pressure to maintain optimum pressure for the conditions of driving.
The high-pressure pump used in the fuel system of the GDI engine may generally includes a plunger, a control valve, and a solenoid valve.
The high-pressure pump pressurizes the fuel while the plunger vertically reciprocates with the operation of the fuel pump cam. The pressure that compresses the fuel is controlled in accordance with when the control valve, which is an inlet valve, closes between the top dead center and the bottom dead center of the plunger. When the pressure that compresses the fuel reaches a predetermined pressure or more, an outlet valve that mechanically operates opens and high-pressure fuel moves to the injectors.
Therefore, the fuel can be discharged only when the control valve that is an inlet valve is closed, such that the control unit controls the discharge amount and the pressure of the fuel by controlling the closing time of the control valve, using a solenoid.
When ignition of the engine is stopped (IGNITION OFF) by stopping the engine, the high-pressure pump stops (OFF) within 0.1 second. When the high-pressure pump stops, the control valve is fully open, such that the fuel pressurized in the high-pressure pump flows backward into the high-pressure pump.
Therefore, vibration and noise are generated by pressure pulsation of the fuel flowing backward into the low-pressure pump, such that NVH (Noise Vibration Harshness) is deteriorated.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.